A passenger on a plane en route to Denver was taken into custody after he claimed to be carrying a bomb in his backpack, officials said.

Five crew members and 136 passengers aboard a Frontier Airlines flight traveling from Knoxville, Tenn. to Denver were evacuated from the plane onto a remote area of the tarmac at Denver International Airport following the possible security threat Friday evening, Frontier Airlines spokeswoman Kate O'Mally told ABC News.

Nick Dannenberg, who was traveling on Frontier Airlines flight 601 told "Good Morning America" he was seated near the man who reportedly told the flight attendant he had brought a bomb on board.

"The guy across the aisle from me pulled the flight attendant to the side and told her that he had a bomb in his backpack," Dannenberg said. "I can't even describe how fast my heart was beating."

The flight crew took the man's backpack to the back of the plane when they became aware of the potential safety risk, as passengers kept an eye on the passenger until the flight landed safely in Denver.

Meanwhile, children on board the flight were sent to the front of the plane for security purposes. There were three unaccompanied minors on the plane who were moved away from the potential bomb, law enforcement officials told ABC News.

Once grounded, authorities handcuffed and removed the man from the flight.

Passengers then left the aircraft, where they were met by the FBI and the Denver bomb squad on the tarmac.

All of the passengers were interviewed by law enforcement overnight.

The FBI would not comment as to whether or not an explosive device was recovered from the carry on.

Officials have not released the man's name. He is believed to be mentally unstable, a law enforcement official briefed on the case told ABC News.

There has been no decision on whether or not to prosecute the man. That decision will likely be made on Monday, law enforcement officials said.